Responsive design isn’t exactly new, it is quickly becoming a best practice in the UX community. That doesn’t mean that everyone knows what responsive design really means. One can find themselves defining it over, and over again as well as defending its use (or non-use as the case may be). Having some external sources for support are always a help. One to consider is Responsive Design, An Overview. It is one of the best and most succinct summaries of responsive design I’ve seen to date.

From the article:

Responsive design is made possible with the use of three functions:

• Adaptive layout – Uses media queries to modify the design in ways that suit different screen sizes.
• Fluid grid – Uses relative units like percentages instead of fixed-width units like pixels.
• Flexible media/images – Images and other media (like videos) must also be scaled using relative units so they don’t expand beyond their containing element.

It goes on to dispel a few myths and lay out the advantages and disadvantages of responsive design. This is a good article to send to someone who may not fully understand what responsive design is–or isn’t.